Detection of slow atoms in laser spectroscopy of a thin vapor film

Laboratoire de Physique des Lasers, URA 282 du CNRS, Institut Galilée, Université Paris Nord - F-93430 Villetaneuse, France

Received: 11 April 1996
Accepted: 18 June 1996

Abstract

We report on high-resolution single-light-beam transmission spectroscopy through an ultra thin vapor cell (thickness 10–). In addition to the expected Doppler-broadened absorption, a novel sub-Doppler structure is observed under normal incidence irradiation. This structure originates from the optical response of atoms with very small velocity components perpendicular to the cell walls, and is connected with the transient atom excitation regime during the wall-to-wall time of flight. In experiments performed in Cs vapor, the slow mechanism of optical pumping leads, for weak light intensities (10–) and a cell, to a velocity selection equivalent to an effective 1D temperature in the sub-mK range.